1. Field of the Invention
Antimicrobial compounds which interact with environmental and/or cell nucleophiles are potentiated by one or more transition metals mixed with a trilower alkanolamine. The antimicrobial compounds include isothiazolones, preferably alkyl and chloroalkyl 4-isothiazolin-3-one, benzylisothiazolone and n-octyl-4-isothiazolin-3-one alone or in admixture, and also compounds referred to as formaldehyde condensates whose biocidal properties are in part or wholly related to released formaldehyde. The metals are preferably used in the form of a polyfunctional ligand, namely a 1:1 molar complex of the metal with triethanolamine. This complex, which is stable at a broad pH range, effectively delivers the metal cation to nucleophiles, usually amine and/or sulfhydryl compounds (particularly peptides and amino acids) which are produced by the microorganism or are components of the system being protected and which prevent interaction of the microorganism with the antimicrobial agent. The result is prolonged and increased efficacy. Other metal complexes with a trilower alkanolamine can be used.
2. Description of Related Art
Disodium monocopper (II) citrate is a polyfunctional ligand in which the Cu-ligand bond is via oxygen (Maurer and Shringapurey, U.S. Pat. No. 4,129,509 (1978) on copper citrate; and Tauler, R., et al., Inorg. Chem. Acta: 105(2): 165-170 (1985) for copper TEA). Also U.S. Pat. Nos. 4,666,616, 4,608,183, 4,707,282, and 4,708,808 to Rossmoore describe the use of citrate complexes as the polyfunctional ligands.
Distinctions are made between the potentiation of isothiazolone derivatives (U.S. Pat. No. 4,608,183; Intl. Biodetn. 26: 303-313, 1990) in which the biocides are irreversibly inactivated by nucleophiles and the formaldehyde-based biocides (U.S. Pat. No. 4,666,616; Intl. Biodetn. 26:51-61, 1990; Europ. J. Biochem. 62:151-160) in which the enzyme degrading formaldehyde is blocked. In the former the transition metal cation protects the isothiazolone molecule from inactivation by non-critical nucleophiles in and outside the microbial cell allowing the biocide to react with critical nucleophilic sites on the microorganism resulting in lethality. The above referenced patents show that a metal polyfunctional ligand has an advantage over the naked metal cation because of greater stability at neutral and alkaline pHs. The insolubility of the metal hydroxides reduces or eliminates the activity of the metal ions.